Laser May Lead to New Applications in Medicine, Fiber Optics, Laser Machining

Photonics.comAug 2005
TIANJIN, China, Aug. 8 -- A research team in China has demonstrated a new way to produce continuous streams of laser light in a desirable portion of the infrared spectrum. Their achievement provides another potentially useful source of infrared laser light which is used in medicine, video displays, materials processing and spectroscopy.

Rui Zhou and co-workers at Tianjin University in China constructed their infrared laser out of a purple-colored crystal called Nd:YVO4 (neodymium doped yttrium orthovanadate). Nd:YVO4 is a relative of the Nd:YAG crystal which produces high-power laser light for laser surgery, laser machining and physics experiments such as the LIGO (Laser Interferometer Gravitational-Wave Observatory) project, which is searching for the gravitational waves first predicted by Albert Einstein almost 100 years ago.

The researchers’ device produces light by pumping energy into the Nd:YVO4 crystal, which sheds much of the energy in the form of photons. Traveling through the crystal, the photons stimulate other regions of the material to emit photons of the same wavelength. The photons are generated in the crystal. One of the ends acts as a totally reflecting mirror and the other is coated with a high transmitting film. Photons that travel through the film enter an output mirror, called an “output coupler,” which is designed such that they tend to reflect photons with a wavelength of 1386 nm. Therefore, 1386 nm photons tend to bounce back and forth between an end of the crystal which acts as total reflecting mirror and the output coupler, stimulating the production of more 1386 nm photons. Meanwhile, a small portion of the photons continually escapes through the output mirror and produces a continuous beam.

The researchers energize the crystal by using a separate diode laser, similar to those that read compact disks and DVDs. In a technique called “diode-end pumping,” the diode laser’s light travels in the same direction as the infrared laser beam it produces. Compared to the “side-pumping” method, in which the pump laser travels perpendicular to the outgoing laser beam, diode-end pumping has several advantages, such as higher efficiency, good beam quality and a smaller volume for the laser system.

While no unique applications for this specific laser design are envisioned, the researchers believe that the combination of Nd:YVO4’s desirable properties and the usefulness of the 1386 nm wavelength may inspire novel applications.

The researchers' results are reported in the current issue of Optics Express, an open-access journal published by the Optical Society of America. For more information, visit: www.opticsexpress.org